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WO2011094321A2 - Structures de mousse poreuses à base de glucide et procédés associés - Google Patents

Structures de mousse poreuses à base de glucide et procédés associés Download PDF

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Publication number
WO2011094321A2
WO2011094321A2 PCT/US2011/022587 US2011022587W WO2011094321A2 WO 2011094321 A2 WO2011094321 A2 WO 2011094321A2 US 2011022587 W US2011022587 W US 2011022587W WO 2011094321 A2 WO2011094321 A2 WO 2011094321A2
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Prior art keywords
starch
nanoparticles
water
solution
precipitate
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Ceased
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PCT/US2011/022587
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WO2011094321A3 (fr
Inventor
Khaled El-Tahlawy
Renzo Shamey
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North Carolina State University
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North Carolina State University
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Publication of WO2011094321A3 publication Critical patent/WO2011094321A3/fr
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L3/00—Compositions of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08L3/02—Starch; Degradation products thereof, e.g. dextrin
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P19/00—Preparation of compounds containing saccharide radicals
    • C12P19/04—Polysaccharides, i.e. compounds containing more than five saccharide radicals attached to each other by glycosidic bonds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2201/00—Foams characterised by the foaming process
    • C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
    • C08J2201/054—Precipitating the polymer by adding a non-solvent or a different solvent
    • C08J2201/0545—Precipitating the polymer by adding a non-solvent or a different solvent from an aqueous solvent-based polymer composition
    • C08J2201/0546—Precipitating the polymer by adding a non-solvent or a different solvent from an aqueous solvent-based polymer composition the non-solvent being organic
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2205/00—Foams characterised by their properties
    • C08J2205/04—Foams characterised by their properties characterised by the foam pores
    • C08J2205/042—Nanopores, i.e. the average diameter being smaller than 0,1 micrometer
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2303/00—Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08J2303/02—Starch; Degradation products thereof, e.g. dextrin

Definitions

  • the presently disclosed subject matter relates to foam structures. Particularly, the presently disclosed subject matter relates to porous, starch-based foam structures and associated methods.
  • the presently disclosed subject matter relates to porous, carbohydrate -based foam structures and related methods.
  • the presently disclosed subject matter can include nanocellular foam structures based on modified starch from renewable natural polymers.
  • the presently disclosed foam structures have unique properties including, but not limited to, significantly increased specific surface area, high degree of brightness and opacity, light weight and porosity which can be used to design and develop a number of mechanisms for the storage and the gradual release of suitable compounds.
  • Foam structures having predefined features, such as particle size and void structure can be provided through estimation and assessment of the composition-structure-processing relationships.
  • the novel, porous, starch-based foam structures disclosed herein may be altered to have a hydrophobic character with associated applications in, including but not limited to, medical, electrical and civil engineering, food, agriculture, and packing industries.
  • a method for producing a porous, starch-based foam structure can include providing a starch solution, which can be precipitated to form starch nanoparticles with a defined void structure.
  • the starch solution can comprise starch slurry of native corn cooked starch or gelatinized starch.
  • native corn cooked starch as described herein, wheat cooked starch or potato cooked starch may be used.
  • the starch solution can comprise water and starch particles. In one example, the starch particles can comprise about 20 percent of the starch solution.
  • the step of precipitating the starch solution can comprise exchanging the water with a solvent having a lower surface tension than the water.
  • the step of exchanging the water with a solvent can be repeated.
  • the starch solution under agitation and prior to the step of precipitating the starch solution, can be heated to thereby produce cooked starch.
  • the starch solution can be heated to about 90 degrees Celsius.
  • Precipitation of the starch solution can include: exchanging the water with ethanol under agitation to thereby form a starch precipitate; and filtering the starch precipitate.
  • the resulting starch particles can be sized between 6 micrometers and 10 micrometers.
  • the starch solution under agitation and prior to the step of precipitating the starch solution, can be heated to thereby produce cooked starch.
  • the step of precipitating the starch solution can comprise: combining the cooked starch with ethanol to thereby form a first emulsion; grinding the cooked starch in the first emulsion to thereby form a starch precipitate; and filtering the starch precipitate.
  • the resulting starch particles can be sized between 3 micrometers and 8 micrometers.
  • the starch solution under agitation and prior to the step of precipitating the starch solution, can be heated to thereby produce cooked starch.
  • the step of precipitating the starch solution can comprise: combining the cooked starch with a nonionic surfactant and a solvent, such as, for example, toluene, to thereby form a first solution; agitating the first solution; combining the first solution with anhydrous ethanol to thereby form a starch precipitate; and filtering the starch precipitate.
  • the starch precipitate can also be dried.
  • the starch particles can be sized between 430 nanometers and 4.8 micrometers. Voids in the predefined void structure can have a diameter of about 140 nanometers.
  • the starch can be gelatinized in the starch solution by combining the starch solution with an alkali such as sodium hydroxide.
  • the step of precipitating the starch solution can comprise: exchanging the water with ethanol under agitation to thereby form a starch precipitate; and filtering the starch precipitate.
  • Voids in the predefined void structure can have a diameter of about 30 to 90 nanometers.
  • the starch particles can be sized between about 5.0 micrometers and 10.2 micrometers.
  • the starch can be gelatinized in the starch solution by combining the starch solution with an alkali such as sodium hydroxide.
  • the step of precipitating the starch solution can comprise: combining the gelatinized starch with a nonionic surfactant and a solvent to thereby form a first solution; agitating the first solution; combining the first solution with anhydrous ethanol to thereby form a starch precipitate; and filtering the starch precipitate.
  • the starch particles can be sized between about 600 nanometers and 5.7 micrometers.
  • the starch can be gelatinized in the starch solution by combining the starch solution with an alkali such as sodium hydroxide.
  • the step of precipitating the starch solution can comprise: combining the gelatinized starch with a nonionic surfactant and a solvent to thereby form a first solution; agitating the first solution; combining the first solution with anhydrous ethanol to thereby form a starch precipitate; neutralizing the first solution with an acid such as HC1; and filtering the starch precipitate.
  • the starch particles can be sized between about 390 nanometers and 3.6 micrometers.
  • a porous, starch-based foam structure is provided.
  • FIG. 1 depicts a flowchart representing a method for producing a porous, starch-based foam structure according to one or more embodiments of the disclosed subject matter
  • FIG. 2 depicts a flowchart representing a method for producing a porous, starch-based foam structure according to one or more embodiments of the disclosed subject matter
  • FIG. 3 depicts a flowchart representing a method for producing a porous, starch-based foam structure according to one or more embodiments of the disclosed subject matter
  • FIGS. 4(a) and 4(b) are Field Emission Scanning Electron Microscopy (FESEM) images of cooked Starch Micro -Cellular Foam (SMCF) particles using mechanical stirring to induce the precipitation process at two different magnifications: 0.5 K, as shown in FIG. 4(a); and 25 K, as shown in FIG. 4(b);
  • FESEM Field Emission Scanning Electron Microscopy
  • FIGS. 5(a) and 5(b) are FESEM images of cooked starch SMCF particles using the ball mill technique during the solvent exchange process at two different magnifications: 0.5 K, as shown in FIG. 5(a); and 50 K, as shown in FIG. 5(b);
  • FIGS. 6(a) and 6(b) are Scanning Electron Microscopy (SEM) images of cooked Starch Microcellular Foam (SMCF) particles using micro-emulsion technique at two different magnifications: 0.1, as shown in FIG. 6(a); and 15 K, as shown in FIG. 6(b);
  • FIGS. 7(a) and 7(b) are FESEM images of NaOH-gelatinized starch SMCF particles using mechanical stirring in the precipitation process at two different
  • magnifications 0.5 K, as shown in FIG. 7(a); and 50 K, as shown in FIG. 7(b);
  • FIGS. 8(a) and 8(b) are FESEM images of NaOH-gelatinized starch SMCF particles using the micro-emulsion technique at different magnifications: IK, as shown in FIG. 8(a); and 75 K, as shown in FIG. 8(b);
  • FIGS. 9(a) and 9(b) are FESEM images of gelatinized starch SMCF particles using the micro-emulsion technique after neutralization of NaOH-with HCl at two different magnifications: 0.5 K, as shown in FIG. 9(a); and 30 K, as shown in FIG. 9(b); and
  • FIGS. 10(a) and 10(b) are FESEM images of neutralized SMCF particles stirred for one hour at 2000 revolutions per minute at two different magnifications: 5 K, as shown in FIG. 10(a); and 20 K, as shown in FIG. 10(b).
  • step may be used herein to connote different aspects of methods employed, the term should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly described.
  • Porous carbohydrate-based foam structures such as those based on starch, as disclosed herein can be produced by precipitating, for example, a starch solution to form starch nanoparticles having a predefined void structure.
  • the physical and chemical properties of the presently disclosed foam structures can be assessed to develop compounds based on natural starch polymers, which are readily available as a renewable natural polymer. These natural bio-compounds can be used as viable alternative products to synthetic petroleum based compounds with enhanced and improved properties. Additionally, the structures disclosed herein are also applicable to water soluble synthetic polymers.
  • novel foam structures or compounds can be produced from water soluble polymers and inexpensive natural bio materials, including but not limited to, starch, water soluble cellulose, chitosan, sodium alginate, hemicelluloses, proteins, polyvinyl alcohols, and, in some instances, synthetic materials such as water soluble synthetic polymers.
  • water soluble polymers and inexpensive natural bio materials including but not limited to, starch, water soluble cellulose, chitosan, sodium alginate, hemicelluloses, proteins, polyvinyl alcohols, and, in some instances, synthetic materials such as water soluble synthetic polymers.
  • the compounds can have applications in several fields of engineering including civil, for example, for the use of light weight construction materials and composites, electrical, for example, for the use of materials having increased specific surface area and high opacity and brightness, agriculture, for example, for the use of host materials for release of suitable compounds, waste water treatment, paper, textiles, packaging, coating and paint industry, for example, as a filler material, as well as medical and pharmaceutical applications, for example, as a host material for the release of medical materials or as a bone replacement composite.
  • civil for example, for the use of light weight construction materials and composites
  • electrical for example, for the use of materials having increased specific surface area and high opacity and brightness
  • agriculture for example, for the use of host materials for release of suitable compounds, waste water treatment, paper, textiles, packaging, coating and paint industry, for example, as a filler material, as well as medical and pharmaceutical applications, for example, as a host material for the release of medical materials or as a bone replacement composite.
  • starch is a high molecular weight polymer of
  • anhydroglucose units C 6 H 10 O 5 linked by alpha-D-glycosidic bonds.
  • Starch the principle carbohydrate storage biopolymer of plants, is an abundant, low cost resource. Starch is synthesized in plant cells as a food reserve. Starch can range from purely linear to extensively branched structures. As the granules populate, the molecules have the potential to form glycosidic conformations characteristic of helices or crystalline order. Starch is composed of two major molecules, amylose and amylopectin. Amylose is defined as a linear molecule but it is recognized that some molecules are slightly branched by (l-6)-i ⁇ -linkages.
  • Amylopectin is a branched polysaccharide constructed from hundreds of short (l-4)-i— >-glucan chains, which are interlinked by (l-6)-i ⁇ -hnkages. Amylopectin is primarily responsible for the granule structure and crystallinity in most starches.
  • Hydrophobic grafted starch nanoparticles can be produced by graft
  • the AOT can form thermodynamic water droplets surrounded by a surfactant monolayer in oil, such as, for example, isooctane.
  • a surfactant monolayer in oil such as, for example, isooctane.
  • Water entrapped within the reverse micelles resembles the polar pockets in cell. This increases the dissolution of the entrapped enzyme within the reverse micelles in nonpolar media and consequently facilitates productive collisions and reactions between enzymes and nonpolar substrate.
  • the starch nanoparticles can be esterified using Candida Antartica Lipase B (CAL-B) as a catalyst in both its immobilized (Novozym 435) and free (SP-525) forms.
  • CAL-B Candida Antartica Lipase B
  • the starch particles can be acylated by formation of Aerosol-OT [AOT, bis(2-ethylhexyl) sodium sulfosuccinate] stabilized micro-emulsions.
  • Aerosol-OT AOT, bis(2-ethylhexyl) sodium sulfosuccinate
  • Starch nanoparticles can be reacted with vinyl stearate, caprolactone, and maleic acid at 40 degrees Celsius for 48 hours with a degree of substitution of 0.8, 0.6, and 0.4, respectively.
  • IF Integral Field
  • precipitation is a process by which a solid is formed in a solution or inside another solid during a chemical reaction or by diffusion in a solid.
  • the solid formed is known as the precipitate
  • the liquid remaining above the solid is known as the supernate.
  • microemulsions can be clear, stable, isotropic, liquid mixtures of oil, water and surfactant.
  • the aqueous phase may contain salt(s) and/or other ingredients, and the oil may be a complex mixture of different hydrocarbons and olefins.
  • microemulsions can form upon simple mixing of the components and do not require the high shear conditions generally used in the formation of ordinary emulsions.
  • Two basic types of microemulsions include direct such as oil dispersed in water and reversed such as water dispersed in oil.
  • TRITON X-100 ® (Ci 4 H 22 0(C 2 H 4 0) n ) is a nonionic surfactant which has a hydrophilic polyethylene oxide group and a hydrocarbon lipophilic or hydrophobic group.
  • non-polar organic solvent such as toluene, also known as methylbenzene, or toluol
  • toluene also known as methylbenzene, or toluol
  • aromatic hydrocarbon used as a solvent.
  • Other organic solvents may also be employed with the embodiments described herein.
  • nanoparticles can be solid, colloidal particles which can consist of macromolecular substances that vary in size from one to 1,000 nanometers.
  • Nanoparticles can be obtained with different properties. Nanoparticles can be used as host compounds and their release characteristics for the encapsulated therapeutic agents can be regulated based on the production method.
  • a method 100 for producing a porous, starch-based foam structure is depicted in the flowchart of FIG. 1.
  • the method 100 includes providing a starch solution 110 and precipitating the starch solution to form starch nanoparticles that define a void structure.
  • a method 200 for producing a porous, starch-based foam structure is depicted in the flowchart of FIG. 2.
  • the method 200 includes providing a starch solution 210, under agitation, heating the starch solution to produce a cooked starch 220, and precipitating the starch solution to form starch nanoparticles that define a void structure 230.
  • Agitation of the starch solution may be effectuated by any manner known in the art, and in one or more embodiments, may include using a mechanical or magnetic stirrer, using a ball mill, and stirring or agitating at varying speeds, intensities, and frequencies. Other manners of agitating the starch solution are described herein. Heating the starch solution 220 may also be effectuated by introducing the solution to heat in a variety of manners described herein.
  • Precipitating the starch solution 230 may be effectuated by, for example, exchanging water of the starch solution with a solvent having a lower surface tension than the water, and may further include repeating the exchanging step. Precipitating the starch solution 230 may also be effectuated by, for example, exchanging water of the starch solution with ethanol under agitation and filtering the starch precipitate. Precipitating the starch solution 230 may also be effectuated by, for example, combining a cooked starch with anhydrous ethanol, grinding the cooked starch to form a starch precipitate, and filtering the starch precipitate.
  • Precipitating the starch solution 230 may also be effectuated by combining a cooked starch with a nonionic surfactant and a solvent to form a first emulsion, agitating the first emulsion, combining the first emulsion with anhydrous ethanol to form a starch precipitate, and filtering the starch precipitate.
  • Other manners of precipitating the starch solution 230 are described herein.
  • a method 300 for producing a porous, starch-based foam structure is depicted in the flowchart of FIG. 3.
  • the method 300 includes providing a starch solution 310, gelatinizing starch in the starch solution by combining the starch solution with an alkali 320, and precipitating the starch solution to form starch nanoparticles that define a void structure 330.
  • Gelatinizing starch in the starch solution by combining the starch solution 310 may be effectuated by, for example, combining the starch solution with an alkali such as sodium hydroxide. Other manners of gelatinizing starch in the starch solution 310 are described herein.
  • Precipitating the starch solution to form starch nanoparticles that define a void structure 330 may be effectuated by, for example, exchanging water of the starch solution with ethanol under agitation and filtering the starch precipitate.
  • Precipitating the starch solution 330 may also be effectuated by, for example, combining the gelatinized starch with a nonionic surfactant and a solvent to form a first emulsion, agitating the first emulsion, combining the first emulsion with anhydrous ethanol to form a starch precipitate, and filtering the starch precipitate.
  • Precipitating the starch solution 330 may also be effectuated by, for example, combining the gelatinized starch with a nonionic surfactant and a solvent to form a first emulsion, agitating the first emulsion, combining the first emulsion with anhydrous ethanol to form a starch precipitate, neutralizing the first emulsion with an acid such as HCL, and filtering the starch precipitate.
  • a nonionic surfactant and a solvent to form a first emulsion
  • agitating the first emulsion combining the first emulsion with anhydrous ethanol to form a starch precipitate
  • neutralizing the first emulsion with an acid such as HCL and filtering the starch precipitate.
  • Other manners of precipitating the starch solution 330 are described herein.
  • Starch nanoparticles may be prepared using a water/oil micro-emulsion technique.
  • starch solution can be mixed with a non-polar organic solvent in the presence of a surfactant to form one phase micro-emulsion solution.
  • the starch nanoparticles can be prepared by crosslinking starch with epichlorohydrin in the presence of n-hexane, and a nonionic surfactant.
  • concentration of starch By increasing the concentration of starch, the diameter of particles can be increased while broadening the distribution of particle size.
  • the range of nanoparticles' diameter can be between 15.6 nanometers to 226 nanometers.
  • Polymers of foam structures have unique physical, mechanical and thermal properties.
  • the properties of foams may be characterized by cell density, expansion ratio, cell size distribution, open cell content, and cell integrity. Different polymers with different properties will form foams having wide varieties of characteristics ranging from soft to stiff modulus, resilient to tough behavior, low to high hysteresis, and mono to multi-model cell distribution.
  • techniques may include freeze-drying, supercritical fluid extrusion, for example using supercritical carbon dioxide, and solvent exchange technique. Each of these techniques is described herein below.
  • Freeze-drying is the process of dehydrating starch and its derivatives under a vacuum, where the moisture content changes directly from a solid to a gaseous form through sublimation without having to undergo the intermediate liquid state. In this process, the product maintains its original size and shape with a minimum cell rupture. Removing moisture prevents the product from deteriorating at room temperature.
  • the freeze drying technique may be used to produce starch microcellular foam with cell size less than 100 micrometers. In this approach, cooked starch is poured in molds and cooled in the refrigerator, and a semi-rigid structure is obtained. The cooked starch is then frozen, during which the water forms ice crystals and is separated from the solute. Freeze drying of the frozen starch sublimates the ice crystals and forms a porous starch cake structure.
  • the physical properties of gelatinized tapioca starch beads may be modified by freeze drying at different temperatures.
  • the bacterial immobilization in freeze-dried tapioca beads may be a simple technique for enhancing delivery of viable probiotics culture to the intestinal tract.
  • Edible bilayer film may be used to coat the dried immobilized beads as an additional protective layer.
  • the thermal conductivities of freeze-dried slabs of starch, gelatin, pectin, cellulose gum, and egg albumen gels have been determined under a variety of conditions, using a guarded hotplate apparatus.
  • the thermal conductivities of dry materials at atmospheric pressure vary from 0.921 x 10 "4 calories centimeters "1 degrees Celsius "1 seconds "1 (gelatin) to 1.337 x 10 "4 for materials such as cellulose gum. In a vacuum, this variation is from 0.218 x 10 "4 for materials such as starch to 0.467 x 10 "4 calories centimeters "1 degrees Celsius "1 seconds "1 for materials such as cellulose gum.
  • the difference between atmospheric pressure and vacuum is equal to the thermal conductivity of air for all the materials except cellulose gum, which gives a greater difference.
  • the thermal conductivity of starch gel increases linearly with increasing temperature from zero to 70 degrees Celsius, and decreases with decreasing pressure, as porous materials normally do, to a constant value below 0.1 millimeters of mercury.
  • a helium atmosphere gives a higher thermal conductivity than air or nitrogen.
  • the thermal conductivity is higher in all freeze- dried gels containing adsorbed water than after the removal of all the water.
  • the thermal conductivity of pectin gels increases with the density. Thermal conductivity is also affected by the type and size of pores of the dried materials. In general, changes in thermal conductivity are significant with pressure, type of gas, and nature of the material, particularly the fibrous structure, but less important with temperature and amount of adsorbed water.
  • Supercritical fluid extrusion is an important field of research in the extrusion industry. This technique has been used for the production of highly expanded biopolymeric foams, such as starch-based polymers, in which carbon dioxide, above its critical pressure of 7.38 megapascals and temperature of 31 degrees Celsius, is used as a blowing agent, a nutrient carrier, and an in-line process modifier.
  • the use of supercritical carbon dioxide (SC-C0 2 ) leads to avoiding the use of steam, shear reduction, and enablement of the use of low production temperatures, such as less than 100 degrees Celsius. These, in turn, offer several advantages over the conventional method of steam puffing including reduced product degradation, decreased machine wear, and the potential for adding heat sensitive nutrients, flavors, and colorants in-line.
  • the SCFX process for starch-based foams may include development of a melt with gas holding rheological properties by gelatinization and mixing of the feed in the extruder barrel, injection of SC-C0 2 loaded with solutes, if desired, into the melt and mixing in the extruder barrel to create a melt-C0 2 solution, pressure drop in the extruder nozzle leading to a thermodynamic instability and consequent nucleation of bubbles, and expansion caused by diffusion of C0 2 into the nucleated bubbles as the extrudate proceeds through the nozzle and immediately after its exit from the nozzle.
  • Starch microcellular foam has been successfully produced with a bubble size in the range of 50 to 200 microns, and bubble density to the order of 106 per cm .
  • the bubble size and expansion ratio of extrudates depends on process and material parameters including C0 2 injection rate, nozzle temperature, oven temperature, melt viscosity, melt yield stress, etc.
  • Production of expanded starch-based foams with microcellular structure can be achieved by injection of supercritical C0 2 into the melt.
  • the high effective diffusivity of C0 2 in the porous matrix may allow for escape of the gas to the environment, reducing the amount available for diffusion into the bubbles, thus posing an important challenge.
  • Several approaches may address this problem such as increasing the nucleation rate and thus the final bubble density in the foam, and reducing the melt temperature.
  • Increasing the nucleation rate may be achieved by decreasing the nozzle diameter in order to achieve a higher pressure drop rate as the starch-C0 2 melt flows through the nozzle.
  • a cooling zone may be used prior to the entry of the melt into the nozzle to assess the feasibility of the second approach.
  • Bubble density can increase more than fourfold when the nozzle radius is decreased from 3.00 to 1.50 millimeters. Higher bubble density can lead to a greater barrier or resistance to diffusion of C0 2 to the environment, and increases expansion ratio by as much as 160 percent. Cooling of the melt also results in a decrease in diffusion coefficient of C0 2 in the starch melt, and thus reduces C0 2 loss to the environment. The expansion ratio is thus increased by 34 percent as the melt temperature is decreased from 60 to 40 degrees Celsius.
  • Starch Microcellular Foam (SMCF) compounds are also disclosed herein and may be produced using a solvent exchange technique from native corn starch crosslinked with glutaraldehyde.
  • the cooked starch solution can be reacted with glutaraldehyde and then precipitated under shear in presence of ethanol.
  • the solvent is exchanged another two times under continuous stirring such as, for example, 2200 revolutions per minute.
  • Nuclear Magnetic Resonance technique can be used to confirm the crosslinking reaction. It has been found that an increase in the glutaraldehyde concentration from zero to 15 grams per 100 grams starch is accompanied by a decrease in particle size, moisture content, brightness, and specific surface area.
  • Biodegradable polymers such as native starch and polylactic acid (PLA) may have commercial applications, such as for packaging materials. Their hydrophilic properties, however, hinder their widespread use in various applications. Hydrophobicity can be improved significantly by acetylating native starch.
  • Acetylated corn starch, with a degree of substitution (DS) 2.3, and acetylated potato starch, with a DS 1.07, may be extruded with 5, 10, or 15 percent PLA in a twin screw co-rotating extruder at 150, 160, or 170 degrees Celsius barrel temperature and 130, 150, or 170 revolutions per minute screw speeds.
  • Analytical techniques including DSC, XRD, and FTIR spectroscopy may be used to analyze the morphological properties of the extruded foams.
  • a central composite response surface design can be used to analyze the effects of acetylated starch type, PLA content, barrel temperature and screw speed on the specific mechanical energy requirements of preparing extruded foams and the radial expansion ratios and compressibility of the extruded foams.
  • test data showed that the glass transition temperature (Tg) and melting temperature (Tm) of corn starch-PLA foams (DS 2.3) were between the Tg and Tm of corn starch and PLA.
  • the Tg's of potato starch-PLA foams were higher than those of acetylated potato starch and PLA, while the Tm's were closer to that of the PLA, when acetylated potato starch was the predominant phase in the blends.
  • XRD showed that both acetylated starch and PLA lost crystallinity during extrusion.
  • the X-ray pattern of the DS 1.07 potato starch-PLA foam was similar to that of potato starch and PLA (DS 1.07).
  • FTIR spectroscopy confirmed no new bonds were formed in either DS 2.3 corn starch-PLA or DS 1.07 potato starch acetate -PLA foams.
  • the type of acetylated starch, PLA content, barrel temperature, and screw speed had significant effects on the specific mechanical energy requirements, radial expansion ratios, and compressibility of the acetylated starch foams.
  • Biodegradable food service packaging including a starch-fiber core and a biodegradable film laminate has been produced.
  • the biodegradable films were made of polylactic acid (PLA), polybutylene succinate/terephthalate (PBST), rubber latex and polybutylene adipate/terephthalate (PBAT).
  • PLA polylactic acid
  • PBST polybutylene succinate/terephthalate
  • PBAT polybutylene adipate/terephthalate
  • This technique involves an in situ process for laminating a baked foam product in a single step.
  • the in situ technique involves a critical element of using a heat insulating fiber sheet to stabilize heat-sensitive laminate films during the baking/lamination process.
  • the PLA-, PBST- and PBAT- laminated samples thus prepared were baked for six minutes at 120 degrees Celsius.
  • the latex-laminated sample which is more heat-stable, does not need to be heat-insulated and can be baked for three minutes at 160 degrees Celsius.
  • Starch- based foam laminated with PLA, PBST or PBAT generally has higher density and greater tensile and flexural strength than the non-laminated counterpart.
  • Starch foam laminated with a rubber latex film was shown to have tensile and flexural properties similar to the non-laminated sample, due to the low modulus and elasticity of the latex film.
  • the in situ lamination process may improve the adhesion of the starch foam core with the fiber sheet, PLA and latex films compared to a post-lamination process. This process may also indicate that all of the laminated materials provided a low water vapor permeance.
  • a comparison of the degradation of treated and unlaminated films in a compost mixture showed that laminated films degraded at a much slower rate compared to native starch.
  • starch may be used for producing a porous, starch-based foam structure in accordance with the presently disclosed subject matter.
  • native corn cooked starch and pre-gelatinized starch may be used.
  • Native cooked starch can be produced by subjecting a starch slurry to continuous stirring and heating at a rate of (1 degree Celsius per minute) to 95 degrees Celsius and keeping it at that temperature for 30 minutes. Starch nanoparticles can be produced through subsequent steps.
  • Pregelatinized starch can be produced by treating Starch slurry with 2 to 5 percent sodium hydroxide solution at room temperature for 30 minutes under continuous stirring. The pH of starch slurry can then be adjusted between four and eight based on the type of crosslinking agents used, which in one or more embodiments, may be
  • epichlorohydrin epichlorohydrin, phosphorous, or oxychloride.
  • Different concentrations of the crosslinking agent can be used to determine the optimum conditions.
  • Crosslinked starch nanoparticles may be produced using a technique employing a water/oil micro-emulsion.
  • Starch micro-emulsion can be prepared in a three necked flask with a mechanical stirrer, condenser, and rubber septum.
  • the preparation technique can be adjusted with 50 milliliter of n-hexane/toluene/isooctane, 10 milliliter of a surfactant such as sorbitan monooleate (Span-80/ bis) (2-ethylhexyl) sulfosuccinate (AOT)/ TRITON X-100 ® (polyoxyethylene-10-isooctylphenyl ether), and a crosslinking agent and aqueous starch solution such as, for example, 20 grams of 10 starch solution.
  • the emulsion can then be subjected to a high shear rate such as, for example, 1000, 2000, 3000, 5000 or 7000 revolutions per minute for 30 minutes.
  • Different parameters can affect particle size formation and extent of crosslinking, such as ratio of water in oil, surfactant concentration, reaction temperature, duration and shear rate.
  • Starch nanoparticles may be precipitated using a solvent exchange technique.
  • solvent of higher surface tension such as, for example water
  • another solvent of lower surface tension such as, for example ethanol, isopropanol, or acetone.
  • This exchange leads to the formation of a foam structure.
  • This process can be repeated to ensure all water molecules are exchanged with ethanol. Optimization of the precipitation process can be employed, since it can be a factor that controls the void structure of the nanoparticles.
  • the starch nanoparticles can be dried at 50 degrees Celsius for four hours before characterization.
  • Two presently disclosed methods may be used to modify starch nanoparticles. These methods may include, for example, enzyme-catalyzed regioselective modification, and chemical catalytic modification.
  • starch nanoparticles can be chemically modified using enzyme as catalyst in nonaqueous medium in the presence of different acylating agents such as, but not limited to, maleic anhydride, butyric anhydride and Palmitic anhydride. Different conditions affecting the modifications process can optimize the esterification reaction.
  • the modified nanoparticles can be filtered, purified and then dried at room temperature.
  • starch nanoparticles can be chemically modified in a non-aqueous medium, such as, for example dimethyl formamide or dimethyl acetamide, in the presence of different alkyl halides, such as, for example octanoyl chloride, benzoyl chloride and palmotyl chloride, as well as dimethyl pyridine as a catalyst.
  • alkyl halides such as, for example octanoyl chloride, benzoyl chloride and palmotyl chloride, as well as dimethyl pyridine as a catalyst.
  • the chemical modification can occur on the surface of the particles which in turn increases the hydrophobicity of the starch particles. Factors affecting the reaction efficiency include, but are not limited to, reaction temperature, acyl chloride concentration, catalyst type and concentration.
  • a solution of 20 percent starch was prepared by introducing 20 grams of starch into a three-necked round flask containing 100 milliliter of distilled water. A mechanical stirrer, septum and condenser were then fixed and the flask was placed in an oil bath. Under continuous stirring, the temperature was raised to 90 degrees Celsius and kept constant for 30 minutes. Finally, the solution containing 20 grams of starch was introduced to a three-necked flask as described below.
  • experiment A-l water was exchanged with ethanol under continuous and vigorous stirring for ten minutes. The precipitate was filtered off and re-introduced into the flask. Another 75 milliliter of anhydrous ethanol was added and the starch paste was stirred at 2400 revolutions per minute for one hour. This step was repeated twice to eliminate all water molecules and ensure a complete exchange with ethanol.
  • A-2 a starch solution of 20 grams was placed inside a 50 milliliter iron cell containing 20 grinding balls. 30 milliliter of ethanol was added. The iron cell was closed and placed in a ball mill machine for 15 minutes. The starch particles were filtered off and placed again in the cell followed by the addition of 50 milliliter of ethanol and the grinding was continued for another 30 minutes. The last step was repeated twice. Finally, the starch was filtered off, washed and then dried at room temperature.
  • A-3 20 grams of cooked starch was added to a three-necked flask containing 50 milliliter of toluene and 15 gram of TRITON X- 100 ® . The solution was stirred for 30 minutes at 2000 revolutions per minute. The micro-emulsion was poured on 100 milliliter of anhydrous ethanol. Starch particles were precipitated immediately and then filtered-off Final washing of starch particles with ethanol can be carried out using a magnetic stirrer for 30 minutes.
  • starch particles were prepared using a solvent exchange technique in which the water molecules are exchanged with a lower surface tension solvent such as ethanol. During the precipitation process, a mechanical stirrer, a ball mill, and a micro-emulsion technique were used.
  • FIGS. 6(a) and (b) show the FESEM micrographs of starch particles obtained from experiment A-2 using a ball mill to precipitate and grind the starch particles to finer particles.
  • a clear foam structure was shown with a slight collapse in the void structure.
  • a mixture of both starch nano- and micro-particles was obtained using the micro-emulsion technique described in experiment A-3.
  • FIGS. 6(a) and (b) show a foam structure with a wide range of particle sizes from 430 nanometers to 4.8 micrometers with an average void diameter of 140 nanometers. The data indicated that the particle size of the SMCF was greatly affected by the technique applied during the solvent exchange precipitation process.
  • experiment B-l the gelatinized starch was allowed to precipitate by mixing 50 milliliter of anhydrous ethanol under vigorous stirring for 10 minutes. Starch particles were filtered-off and washed with ethanol. The starch particles were then transferred to a flask, followed by addition of 75 milliliter ethanol and were stirred at 2400 revolutions per minute for one hour and then filtered. The last step was repeated twice under the same conditions. Finally, the solution was filtered and dried.
  • experiment B-2 20 grams of alkali gelatinized starch was added to a three-necked flask containing 50 milliliter of toluene and 15 grams of TRITON X- 100 ® . The solution was stirred for 30 minutes at 2000 revolutions per minute. The micro-emulsion solution was poured on 100 milliliter of anhydrous ethanol. Starch particles were precipitated immediately and then filtered-off Final washing of starch particles with ethanol was carried out using a magnetic stirrer for 30 minutes.
  • experiment B-3 the gelatinized starch underwent the same procedure as that used in experiment B-2. However, the starch solution was neutralized with Hydrochloric acid (HC1).
  • HC1 Hydrochloric acid
  • Gelatinization of starch with sodium hydroxide was used to dissolve the starch in water. Such an experiment was carried out at room temperature as an alternative to cooking starch at a higher temperature for a longer period, such as, for example, 95 degrees Celsius for 30 minutes. The gelatinization is an economical way to dissolve starch in water.
  • FIGS 7(a), 7(b), 8(a), 8(b), 9(a), and 9(b) show the surface characteristics of starch particles when stirring and micro -emulsion techniques were used to precipitate the starch particles during the solvent exchange technique to exchange the water molecules with ethanol.
  • FESEM micrographs show that all the samples have a foam structure. Results reveal that on average higher particles sizes, 8 micrometers with one to three micrometers void diameter were obtained when the stirring technique was used to precipitate the starch particles as depicted in FIGS. 7(a) and 7(b).
  • Morphological characterization of starch nanocellular foams was carried out on images acquired using a scanning electron microscope (SEM), and the samples were deposited on a 10 nanometers thick platinum plate to make the samples conductive.
  • the void diameters of SNCF apparent on the particle surface were determined using after spatial calibration using the length scale provided with the SEM micrograph. The apparent density values were also obtained.
  • the brightness of the SNCF powder was measured using a computing device and a brightness measurement device to measure the brightness of the SNCF as a function of chemical modification.
  • the surface area of the SNCF was determined with a BET surface area analysis using 30 percent N 2 in Helium gas.
  • FTIR Fourier transform infrared
  • High resolution solid-state NMR is another important tool was used to investigate the molecular structural changes of native and modified starch using a Spectrometer.
  • the CP/MAS experiment may be conducted, for example, on a four millimeter MAS probe.
  • the moisture content of the SNCF was determined using, for example, thermal gravimetric analysis on samples exposed to ambient conditions. The samples were heated to 120 degrees Celsius for 30 minutes at a temperature rate increase of five degrees Celsius per minute.
  • Elemental analysis was performed using an elemental spectrometer. The sample was placed in a tin container, dropped in a furnace with oxygen at 950 degrees Celsius, and the carbon was measured as C0 2 in an infrared cell (IR cell) and the hydrogen was measured as water in an IR cell. The gasses were then swept over hot copper sticks to remove oxygen and reduce the N0 2 to N 2 , the C0 2 and H 2 0 were removed and the N 2 measured by a thermal conductivity cell. The graft yield percent of the modified starch was calculated according to the following equation:
  • C MS is the percent carbon in the modified starch (X percent)
  • C ST is the percent carbon in the dry native starch (Y percent)
  • C M is the theoretical percent C of acylating agent.
  • High resolution solid-state NMR was used to investigate the molecular structural changes of native and crosslinked starch using a spectrometer.
  • the CP/MAS experiment was run on a 4 millimeter MAS probe.

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Abstract

La présente invention a pour objet des structures de mousse poreuses à base de glucide et des procédés associés. Selon un aspect, un procédé peut comprendre l'utilisation d'une solution d'amidon. La solution d'amidon peut être précipitée pour former des nanoparticules d'amidon ayant une structure lacunaire prédéfinie.
PCT/US2011/022587 2010-01-26 2011-01-26 Structures de mousse poreuses à base de glucide et procédés associés Ceased WO2011094321A2 (fr)

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EP3101085A1 (fr) 2015-06-01 2016-12-07 Cytec Industries Inc. Compositions de tensioactifs moussants
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WO2024221618A1 (fr) * 2023-04-26 2024-10-31 浙江大学 Procédé de préparation d'un amidon poreux utilisé dans un emballage probiotique, et application

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FI118179B (fi) * 2003-10-02 2007-08-15 Valtion Teknillinen Pigmentti ja täyteaine sekä menetelmä näiden valmistamiseksi

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CN110714040A (zh) * 2019-10-28 2020-01-21 江南大学 一种树枝状葡糖基纳米颗粒的生物合成方法

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